Hardware:

1802 based computer, built equivalent to Micro/Elf, Elf, Elf II, or Super Elf

Serial Interface equivalent to Giant Board (Q and EF4)

IDE/CF interface

Minimum of 12k ram

Optional memory mapper

Ports:

Port

In

Out

1

Activate Pixie graphics1

Deactivate Pixie graphics1

2

Write disk controller selection port3

3

Read disk controller selected port3

Write disk controller selected port3

4

Read input switches/keypad1

Write data displays1

5

Select memory pager cell to change3

6

Write new memory offset to selected pager cell3

7

Read input ASCII keyboard2

Write output port2

1 Defined by standard Elf system documentation2 As per Giant Board documentation3 Non-standardized ports used by my hardware

EF Lines

EF1

Pixie graphics frame indicator

EF4

Serial IN line

Memory Pager:

This memory mapper works on the principal of the top 4 address lines being used
to access an additional 8 bits of address space stored in a 16x8 memory. This
brings the total address bits to 20 providing 1MB of ram segmented into 256 4k
pages.

The circuit for the memory mapper ignores position 0, thus allowing during
reset the bottom 4k of ram to be available.